Inorganic fillers, such as silica, are believed to impart improved wet traction, rolling resistance, tear strength, snow traction and other performance parameters when used as filler within tire treads. Mixing silica into a tire stock, however, can be difficult because silica particles agglomerate extensively and therefore are not easily dispersed. In addition, silica particles are less compatible than carbon black with rubber molecules. In response, processing and dispersing aids and coupling agents are often used during compounding.
In the art of making tires, it is desirable to employ rubber vulcanizates that demonstrate improved rolling resistance, wet skid resistance, and reduced hysteresis loss at certain temperatures. Factors believed to affect these properties include the degree of filler networking (particle agglomeration), the degree of polymer-filler interaction, the cross-link density of the rubber, and polymer free ends within the cross-linked rubber network.
Because precipitated silica has been increasingly used as reinforcing particulate filler in tires, there is a need to overcome the processing problems associated with silica fillers. Additionally, there is a need to increase polymer-filler interaction in silica-filled tires, thereby improving rolling resistance, wear resistance, and wet skid resistance.